The present application relates to an air belt apparatus for a motor vehicle, provided with an expansion portion corresponding to a head portion of an occupant when the air belt apparatus is inflated.
An air belt apparatus provided with a height position control device, in which a shoulder anchor for guiding a webbing for occupant restraint, provided with an expansion portion, is set to a height position where the same does not face to a side face of a head portion of the occupant at a normal time, and which the shoulder anchor is set to a position where the same faces a side of the head portion of the occupant at a side face collision, is disclosed in Japanese Unexamined Patent Application Publication No. 2001-239906 (incorporated by reference herein). On the other hand, an air belt apparatus, in which a belt guide for guiding a webbing for occupant restraint is fixed to a shoulder portion of a seatback, is disclosed in Japanese Unexamined Patent Application Publication No. 2002-527282 (incorporated by reference herein).
However, when the expansion portion in an air belt is inflated, since internal pressure is uniformly affected in the expansion portion, a cross-sectional shape of the expansion portion ordinarily tends to become a round shape. Accordingly, as in the hitherto known example described in the aforementioned patent publication, when the expansion portion is intended to be laterally enlarged at a side of the head portion of the occupant in an upper and lower direction of the motor vehicle, an expansion diameter of the expansion portion is entirely large sized, and thereby a folded-back thickness of the expansion portion in an ordinary use is increased. Consequently, it has been hard for usability of the webbing for occupant restraint to be preferably maintained.
Further, as in the hitherto known example described in the aforementioned patent publication, when the belt guide having a horizontally long guide hole is fixed to the seatback, the expansion portion is widely expanded in a vehicle-width direction by means of being limited by the guide hole, and therefore it has been hard for the expansion portion to be expanded toward an upper position facing the head portion of an occupant in the vehicle-width direction.